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Mar., 1911 NESTING OF TIlE FORSTER AND BI. ACK TERNS IN COLORADO 61 swerved to barely miss our heads would give utterance to a shrill scream, which, coupled with a sudden booming of the wings, was altogether disconcerting. We often had the birds swoop so close to us that we could plainly feel the rush of air from their wings. A few Black-crowned Night Herons were nesting among the terns, and one unfortunate youngster, unable to fly, who deserted his nest at our approach, took refuge on a tern's nest, where he was promptly attacked by half a dozen of the birds, and although twice as large as his assailants, was knocked down repeatedly, by well directed blows of the birds' wings, until he finally sought safety in the water. We frequently saw the birds flying about with small fish in their bills, and on one occasion a minnow about two inches long was found in a nest contain- ing young. We found one unfortunate bird suspended by the neck, between two upright cat-tail stalks, just above the crotch, on which in its frantic efforts to liberate itself it had sawed its neck paiuful- ly. Our timely arrival prob- ably saved it from a tragic death, as it was almost ex- hausted when we liberated it. BLACK TERi? Also beautiful, and even more interesting to us thm? the Forster Terns because of the mysterious manner in which their breeding grounds eluded our search were the Black Terns ( Hydr. oc]telidon n.surinameusis). These dain- ty little fellows were fully as abundant in point of numbers as the Forster Terns, but al- though we saw numbers of birds on every trip, careful Fig. 27. YOUNG FORSTER TERN ABOUT ONE-THIRD GROWN and thorough searching failed to discover a nest during the breeding season of 1906, and that of 1907 was almost gone, before the coveted prize was discovered. The birds appeared early in May (May 11, 1907, is my earliest record) and a week later were common. On May 17, 1907, one flock of sixty-five birds was seen (apparently migrants), and on May 17, 1908, two flocks of fully one hun- dred birds each were observed at the lakes. Soon after arriving the birds would become wonted to some certain poud or lake, and here amid their threatening screams and complaitats we would splash through waist deep water by the hour, and plow through acres of soft black ooze, and decaying cat-tails, in a fruitless search for the nests. Finally on July 5, 1907, after nearly all the rest of the birds had finished their nesting, and after we had about given up hope of finding the Black Terns' nests at all, the happy discovery was made, and I can do no better than to quote from my note-book of that date. , "There were only four Black Terns on the lake, as near as we could tell, and we worked the whole lake over, and then found the nest by coming back to the